Influence of fluid circulation on in vitro reactivity of bioactive glass particles

The influence of circulation of simulated body fluid (SBF) on the in vitro behavior of glass particles (500–800 μm) was studied for seven glasses by measuring in situ pH inside the particle beds at 37 °C. Reaction layers on particle surfaces were characterized with SEM/EDXA. Differences in the tendency to form reaction layers on surfaces at different locations in the particle beds were determined using samples with interconnected porosity prepared by sintering the particles. Circulation of the solution above the particle bed affected strongly the in vitro behavior of the particles. Due to poor diffusion, the static conditions led to high pH in the SBF within the particle beds and uneven layer formation on the particles. Fluid circulation above the particle beds resulted in a homogenous environment lacking the pronounced pH gradients seen in the static system. The reaction layers on the particles were uniform but thin in the circulating conditions.